This invention relates to a process to reduce catalyst fluidization in catalyst regeneration units. More particularly, this invention relates to the use of ventilated annular baffles to lower the gas velocity of gases exiting continuing catalyst regeneration units (CCR).
Although catalysts for the conversion of hydrocarbons have a tendency to deactivate, usually a catalyst's activity may be restored by one of a number of processes that are known generally as regeneration processes. Regeneration processes are extensively used. The specific steps that comprise a regeneration process depend in part on the reason for the deactivation. For example, if the catalyst contains a catalytic metal such as platinum, regeneration usually includes oxidizing the metal by contacting the catalyst with oxygen. In an oxidized state, however, the catalyst metal is generally not in its most active form for promoting hydrocarbon conversion reactions. Consequently, regeneration often also includes reducing the oxidized metal by contacting the catalyst with hydrogen. Operating conditions and methods for such catalyst reduction steps are well known. Regeneration processes that include a catalyst reduction step can be carried out in situ, or the catalyst may be withdrawn from the vessel in which the hydrocarbon conversion takes place and transported to a separate regeneration zone for reactivation. Arrangements for continuously or semi continuously withdrawing catalyst particles from a reaction zone and for reactivation in a regeneration zone are well known. In one type of regeneration system, there are both upper and lower reduction zones where the upper reduction gases and lower reduction gases combine to exit the catalyst bed between an upper cylindrical baffle and the shell of the reduction zone vessel. It has been found that the gas velocity of the combined reduction gas flow can be too high which can result in catalyst attrition and clogging of vent gas lines.